In a hard disk manufacturing process, a plurality of thin films are continuously deposited on the two principal surfaces of an insulating substrate at the same time. More specifically, after an underlayer made of a metal film is deposited, a magnetic layer is deposited by applying a bias voltage to the underlayer. As a deposition apparatus to be used when the step of continuously depositing a plurality of thin films includes the bias voltage application deposition step, an apparatus including a substrate shift chamber and substrate shift mechanism is disclosed in patent reference 1. FIG. 5 is an exemplary view of the main parts of this apparatus.
In this apparatus, a substrate holder includes a main body 21 and a plurality of substrate supporting pawls 23a and 23b, and holds an insulating substrate 22 such that the two principal surfaces are parallel to the vertical direction. After an underlayer made of a metal film is deposited on the substrate 22, a substrate shift mechanism 31 holds the substrate 22 held by the substrate holder, and a release mechanism (not shown) pushes down the substrate supporting pawl 23b, thereby releasing the substrate 22 from the substrate supporting pawls 23a and 23b. After that, the substrate 22 is supported again as it is rotated so that the substrate supporting pawls 23a and 23b are positioned on the underlayer deposition surface, thereby electrically connecting the underlayer on the substrate 22 and the main body 21 of the substrate holder. This substrate holder is moved to a deposition chamber for performing the bias voltage application step, and an electrode mover (not shown) of a bias voltage application electrode is brought into contact with the main body 21 of the substrate holder. The next deposition is performed by applying a bias voltage to the underlayer via the main body 21 and substrate supporting pawls 23a and 23b. 
In the apparatus described in patent reference 1, however, the substrate 22 is transferred from the substrate holder to the substrate shift mechanism 31 after once the underlayer is deposited, and supported by the substrate holder again after being rotated. Therefore, the substrate may fall when it is transferred or supported again as described above. Also, the substrate shift mechanism 31 has a complicated structure, so a specialized vacuum chamber including the mechanism is necessary. This increases the size of the whole apparatus.
As apparatuses having solved this problem, patent references 2 to 4 have disclosed apparatuses in which a bias voltage application pawl is prepared in addition to substrate supporting pawls of a substrate holder, and deposition is performed by bringing the bias voltage application pawl into contact with a substrate in only the bias voltage application deposition step. FIGS. 6A, 6B, 7A, and 7B are exemplary views of substrate holders of these apparatuses.
A substrate holder shown in FIGS. 6A and 6B includes a main body 41, a plurality of substrate supporting pawls 43, and a specialized bias voltage application pawl 44. This apparatus has a structure in which all the substrate supporting pawls 43 are in contact with a substrate 42, and a mechanism (not shown) pushes down the specialized bias voltage application pawl 44 when depositing an underlayer (FIG. 6A). After that, the specialized bias voltage application pawl 44 is brought into contact with the underlayer by releasing the mechanism having pushed down the specialized bias voltage application pawl 44, and deposition is performed by applying a bias voltage from a bias voltage source 45 to the underlayer via the specialized bias voltage application pawl 44 (FIG. 6B).
Also, a substrate holder shown in FIGS. 7A and 7B includes a main body 51, a plurality of substrate supporting pawls 53, and a specialized bias voltage application pawl 54. In this apparatus, a substrate 52 is normally supported by the substrate supporting pawls 53 alone, and the specialized bias voltage application pawl 54 is separated from the substrate (FIG. 7A). An underlayer is deposited in this state. In the bias voltage application deposition step after that, a bias voltage supply bar 56 pushes down the specialized bias voltage application pawl 54 and brings it into contact with the underlayer (FIG. 7B). In this state, deposition is performed by applying a bias voltage from a bias voltage source 55 to the underlayer via the bias voltage supply bar 56 and specialized bias voltage application pawl 54.    Patent reference 1: Japanese Patent Laid-Open No. 7-243037    Patent reference 1: Japanese Patent Laid-Open No. 2003-521792    Patent reference 3: Japanese Patent No. 3002632    Patent reference 4: Japanese Patent No. 2926740